#!/usr/bin/python3
# Authors: Martin Kosek <mkosek@redhat.com>
#
# Copyright (C) 2011  Red Hat
# see file 'COPYING' for use and warranty information
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.
#

from __future__ import print_function

import logging

from ipapython import ipachangeconf
from ipapython.config import IPAOptionParser
from ipapython.dn import DN
from ipapython import version
from ipapython import ipautil, certdb
from ipalib import api, errors, x509
from ipalib.constants import FQDN
from ipaserver.install import installutils
# pylint: disable=deprecated-module
from optparse import OptionGroup, OptionValueError
# pylint: enable=deprecated-module
from ipapython.ipa_log_manager import standard_logging_setup
import copy
import sys
import os
import signal
import tempfile
import select
import socket
import time
import threading
import traceback
from socket import SOCK_STREAM, SOCK_DGRAM
import distutils.spawn
from ipaplatform.paths import paths
import gssapi

logger = logging.getLogger(os.path.basename(__file__))

CONNECT_TIMEOUT = 5
RESPONDER = None
QUIET = False
CCACHE_FILE = None
KRB5_CONFIG = None


class SshExec:
    def __init__(self, user, addr):
        self.user = user
        self.addr = addr
        self.cmd = distutils.spawn.find_executable('ssh')
        # Bail if ssh is not installed
        if self.cmd is None:
            raise RuntimeError("ssh not installed")

    def __call__(self, command, verbose=False):

        tmpf = tempfile.NamedTemporaryFile()
        cmd = [
            self.cmd,
            '-o StrictHostKeychecking=no',
            '-o UserKnownHostsFile=%s' % tmpf.name,
            '-o GSSAPIAuthentication=yes',
            '-o User=%s' % self.user,
            '%s' % self.addr,
            command
        ]
        if verbose:
            cmd.insert(1, '-v')

        env = dict()
        if KRB5_CONFIG is not None:
            env['KRB5_CONFIG'] = KRB5_CONFIG
        elif 'KRB5_CONFIG' in os.environ:
            env['KRB5_CONFIG'] = os.environ['KRB5_CONFIG']
        if CCACHE_FILE is not None:
            env['KRB5CCNAME'] = CCACHE_FILE
        elif 'KRB5CCNAME' in os.environ:
            env['KRB5CCNAME'] = os.environ['KRB5CCNAME']

        return ipautil.run(cmd, env=env, raiseonerr=False,
                           capture_output=True, capture_error=True)


class CheckedPort:
    def __init__(self, port, port_type, description):
        self.port = port
        self.port_type = port_type
        self.description = description


BASE_PORTS = [
                CheckedPort(389, SOCK_STREAM, "Directory Service: Unsecure port"),
                CheckedPort(636, SOCK_STREAM, "Directory Service: Secure port"),
                CheckedPort(88, SOCK_STREAM, "Kerberos KDC: TCP"),
                CheckedPort(88, SOCK_DGRAM, "Kerberos KDC: UDP"),
                CheckedPort(464, SOCK_STREAM, "Kerberos Kpasswd: TCP"),
                CheckedPort(464, SOCK_DGRAM, "Kerberos Kpasswd: UDP"),
                CheckedPort(80, SOCK_STREAM, "HTTP Server: Unsecure port"),
                CheckedPort(443, SOCK_STREAM, "HTTP Server: Secure port"),
             ]


def parse_options():
    def ca_cert_file_callback(option, opt, value, parser):
        if not os.path.exists(value):
            raise OptionValueError(
                "%s option '%s' does not exist" % (opt, value))
        if not os.path.isfile(value):
            raise OptionValueError(
                "%s option '%s' is not a file" % (opt, value))
        if not os.path.isabs(value):
            raise OptionValueError(
                "%s option '%s' is not an absolute file path" % (opt, value))

        try:
            x509.load_certificate_list_from_file(value)
        except Exception:
            raise OptionValueError(
                "%s option '%s' is not a valid certificate file" %
                (opt, value))

        parser.values.ca_cert_file = value

    parser = IPAOptionParser(version=version.VERSION)

    replica_group = OptionGroup(parser, "on-replica options")
    replica_group.add_option("-m", "--master", dest="master",
                      help="Master address with running IPA for output connection check")
    replica_group.add_option("-a", "--auto-master-check", dest="auto_master_check",
                      action="store_true",
                      default=False,
                      help="Automatically execute connection check on master")
    replica_group.add_option("-r", "--realm", dest="realm",
                      help="Realm name")
    replica_group.add_option("-k", "--kdc", dest="kdc",
                      help="Master KDC. Defaults to master address")
    replica_group.add_option("-p", "--principal", dest="principal",
                      default=None, help="Principal to use to log in to remote master")
    replica_group.add_option("-w", "--password", dest="password", sensitive=True,
                      help="Password for the principal")
    replica_group.add_option("--ca-cert-file", dest="ca_cert_file",
                             type="string", action="callback",
                             callback=ca_cert_file_callback,
                             help="load the CA certificate from this file")
    parser.add_option_group(replica_group)


    master_group = OptionGroup(parser, "on-master options")
    master_group.add_option("-R", "--replica", dest="replica",
                      help="Address of remote replica machine to check against")
    parser.add_option_group(master_group)

    common_group = OptionGroup(parser, "common options")
    common_group.add_option("-c", "--check-ca", dest="check_ca",
                      action="store_true",
                      default=False,
                      help="Check also ports for Certificate Authority "
                        "(for servers installed before IPA 3.1)")

    common_group.add_option("", "--hostname", dest="hostname",
                      help="The hostname of this server (FQDN). "
                           "By default the result of getfqdn() call from "
                           "Python's socket module is used.")
    parser.add_option_group(common_group)

    parser.add_option("-d", "--debug", dest="debug",
                      action="store_true",
                      default=False, help="Print debugging information")
    parser.add_option("-q", "--quiet", dest="quiet",
                      action="store_true",
                      default=False, help="Output only errors")
    parser.add_option("--no-log", dest="log_to_file", action="store_false",
                      default=True, help="Do not log into file")

    options, _args = parser.parse_args()
    safe_options = parser.get_safe_opts(options)

    if options.master and options.replica:
        parser.error("on-master and on-replica options are mutually exclusive!")

    if options.master:
        if options.auto_master_check and not options.realm:
            parser.error("Realm is parameter is required to connect to remote master!")
        if not os.getegid() == 0:
            parser.error("You can only run on-replica part as root.")

    if options.master and not options.kdc:
       options.kdc = options.master

    if not options.master and not options.replica:
       parser.error("No action: you should select either --replica or --master option.")

    if not options.hostname:
        options.hostname = FQDN

    return safe_options, options


def logging_setup(options):
    log_file = None

    if os.getegid() == 0 and options.log_to_file:
        log_file = paths.IPAREPLICA_CONNCHECK_LOG

    standard_logging_setup(log_file, verbose=(not options.quiet),
                           debug=options.debug, console_format='%(message)s')


def sigterm_handler(signum, frame):
    # do what SIGINT does (raise a KeyboardInterrupt)
    sigint_handler = signal.getsignal(signal.SIGINT)
    if callable(sigint_handler):
        sigint_handler(signum, frame)


def configure_krb5_conf(realm, kdc, filename):

    krbconf = ipachangeconf.IPAChangeConf("IPA Installer")
    krbconf.setOptionAssignment((" = ", " "))
    krbconf.setSectionNameDelimiters(("[","]"))
    krbconf.setSubSectionDelimiters(("{","}"))
    krbconf.setIndent(("","  ","    "))

    opts = [{'name':'comment', 'type':'comment', 'value':'File created by ipa-replica-conncheck'},
            {'name':'empty', 'type':'empty'}]

    #[libdefaults]
    libdefaults = [{'name':'default_realm', 'type':'option', 'value':realm}]
    libdefaults.append({'name':'dns_lookup_realm', 'type':'option', 'value':'false'})
    libdefaults.append({'name':'dns_lookup_kdc', 'type':'option', 'value':'true'})
    libdefaults.append({'name':'rdns', 'type':'option', 'value':'false'})
    libdefaults.append({'name':'ticket_lifetime', 'type':'option', 'value':'24h'})
    libdefaults.append({'name':'forwardable', 'type':'option', 'value':'true'})
    libdefaults.append({'name':'udp_preference_limit', 'type':'option', 'value':'0'})

    opts.append({'name':'libdefaults', 'type':'section', 'value': libdefaults})
    opts.append({'name':'empty', 'type':'empty'})

    #the following are necessary only if DNS discovery does not work
    #[realms]
    realms_info =[{'name':'kdc', 'type':'option', 'value':ipautil.format_netloc(kdc, 88)},
                 {'name':'master_kdc', 'type':'option', 'value':ipautil.format_netloc(kdc, 88)},
                 {'name':'admin_server', 'type':'option', 'value':ipautil.format_netloc(kdc, 749)}]
    realms = [{'name':realm, 'type':'subsection', 'value':realms_info}]

    opts.append({'name':'realms', 'type':'section', 'value':realms})
    opts.append({'name':'empty', 'type':'empty'})

    #[appdefaults]
    pamopts = [{'name':'debug', 'type':'option', 'value':'false'},
               {'name':'ticket_lifetime', 'type':'option', 'value':'36000'},
               {'name':'renew_lifetime', 'type':'option', 'value':'36000'},
               {'name':'forwardable', 'type':'option', 'value':'true'},
               {'name':'krb4_convert', 'type':'option', 'value':'false'}]
    appopts = [{'name':'pam', 'type':'subsection', 'value':pamopts}]
    opts.append({'name':'appdefaults', 'type':'section', 'value':appopts})

    logger.debug("Writing temporary Kerberos configuration to %s:\n%s",
                 filename, krbconf.dump(opts))

    krbconf.newConf(filename, opts)


class PortResponder(threading.Thread):

    PROTO = {socket.SOCK_STREAM: 'tcp',
             socket.SOCK_DGRAM: 'udp'}

    def __init__(self, ports):
        """
        ports: a list of CheckedPort
        """
        super(PortResponder, self).__init__()
        # copy ports to avoid the need to synchronize it between threads
        self.ports = copy.deepcopy(ports)
        self._sockets = []
        self._close = False
        self._close_lock = threading.Lock()
        self.responder_data = b'IPA'
        self.ports_opened = False
        self.ports_open_cond = threading.Condition()

    def run(self):
        logger.debug('Starting listening thread.')

        for port in self.ports:
            self._bind_to_port(port.port, port.port_type)
        with self.ports_open_cond:
            self.ports_opened = True
            logger.debug('Ports opened, notify original thread')
            self.ports_open_cond.notify()

        while not self._is_closing():
            ready_socks, _socks1, _socks2 = select.select(
                self._sockets, [], [], 1)
            if ready_socks:
                ready_sock = ready_socks[0]
                self._respond(ready_sock)

        for sock in self._sockets:
            port = sock.getsockname()[1]
            proto = PortResponder.PROTO[sock.type]
            sock.close()
            logger.debug('%d %s: Stopped listening', port, proto)

    def _is_closing(self):
        with self._close_lock:  # pylint: disable=not-context-manager
            return self._close

    def _bind_to_port(self, port, socket_type):
        # Use IPv6 socket as it is able to accept both IPv6 and IPv4
        # connections. Since IPv6 kernel module is required by other
        # parts of IPA, it should always be available.
        family = socket.AF_INET6
        host = '::'   # all available interfaces
        proto = PortResponder.PROTO[socket_type]

        try:
            sock = socket.socket(family, socket_type)

            # Make sure IPv4 clients can connect to IPv6 socket
            sock.setsockopt(socket.IPPROTO_IPV6, socket.IPV6_V6ONLY, 0)

            if socket_type == socket.SOCK_STREAM:
                sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)

            sock.bind((host, port))
            if socket_type == socket.SOCK_STREAM:
                # There might be a delay before accepting the connection,
                # because a single thread is used to handle all the
                # connections. Thus a backlog size of at least 1 is needed.
                sock.listen(1)

            logger.debug('%d %s: Started listening', port, proto)
        except socket.error:
            logger.warning('%d %s: Failed to bind', port, proto)
            logger.debug("%s", traceback.format_exc())
        else:
            self._sockets.append(sock)

    def _respond(self, sock):
        port = sock.getsockname()[1]
        if sock.type == socket.SOCK_STREAM:
            connection, addr = sock.accept()
            try:
                connection.sendall(self.responder_data)
                logger.debug('%d tcp: Responded to %s', port, addr[0])
            finally:
                connection.close()
        elif sock.type == socket.SOCK_DGRAM:
            _data, addr = sock.recvfrom(1)
            sock.sendto(self.responder_data, addr)
            logger.debug('%d udp: Responded to %s', port, addr[0])

    def stop(self):
        logger.debug('Stopping listening thread.')

        with self._close_lock:  # pylint: disable=not-context-manager
            self._close = True


def port_check(host, port_list):
    ports_failed = []
    ports_udp_warning = []  # conncheck could not verify that port is open
    log_level = {
        SOCK_DGRAM: logging.WARNING,
        SOCK_STREAM: logging.ERROR
    }
    for port in port_list:
        try:
            port_open = ipautil.host_port_open(
                host, port.port, port.port_type,
                socket_timeout=CONNECT_TIMEOUT, log_errors=True,
                log_level=log_level[port.port_type])
        except socket.gaierror:
            raise RuntimeError("Port check failed! Unable to resolve host name '%s'" % host)
        if port_open:
            result = "OK"
        else:
            if port.port_type == socket.SOCK_DGRAM:
                ports_udp_warning.append(port)
                result = "WARNING"
            else:
                ports_failed.append(port)
                result = "FAILED"
        logger.info("   %s (%d): %s", port.description, port.port, result)

    if ports_udp_warning:
        logger.warning(
            ("The following UDP ports could not be verified as open: %s\n"
             "This can happen if they are already bound to an application\n"
             "and ipa-replica-conncheck cannot attach own UDP responder."),
            ", ".join(str(port.port) for port in ports_udp_warning))

    if ports_failed:
        msg_ports = []
        for port in ports_failed:
            port_type_text = "TCP" if port.port_type == SOCK_STREAM else "UDP"
            msg_ports.append('%d (%s)' % (port.port, port_type_text))
        raise RuntimeError("Port check failed! Inaccessible port(s): %s" \
                % ", ".join(msg_ports))


def main():
    global RESPONDER
    safe_options, options = parse_options()

    logging_setup(options)
    logger.debug('%s was invoked with options: %s', sys.argv[0], safe_options)
    logger.debug("missing options might be asked for interactively later\n")
    logger.debug('IPA version %s', version.VENDOR_VERSION)

    signal.signal(signal.SIGTERM, sigterm_handler)

    required_ports = BASE_PORTS
    if options.check_ca:
        # Check old Dogtag CA replication port
        # New installs with unified databases use main DS port (checked above)
        required_ports.append(CheckedPort(7389, SOCK_STREAM,
                                          "PKI-CA: Directory Service port"))

    if options.replica:
        logger.info("Check connection from master to remote replica '%s':",
                    options.replica)
        port_check(options.replica, required_ports)
        logger.info("\nConnection from master to replica is OK.")

    # kinit to foreign master
    if options.master:
        # check ports on master first
        logger.info("Check connection from replica to remote master '%s':",
                    options.master)
        tcp_ports = [ port for port in required_ports if port.port_type == SOCK_STREAM ]
        udp_ports = [ port for port in required_ports if port.port_type == SOCK_DGRAM ]
        port_check(options.master, tcp_ports)

        if udp_ports:
            logger.info("\nThe following list of ports use UDP protocol "
                        "and would need to be\n"
                        "checked manually:")
            for port in udp_ports:
                result = "SKIPPED"
                logger.info("   %s (%d): %s",
                            port.description, port.port, result)

        logger.info("\nConnection from replica to master is OK.")

        # create listeners
        logger.info("Start listening on required ports for remote "
                    "master check")

        RESPONDER = PortResponder(required_ports)
        RESPONDER.start()

        with RESPONDER.ports_open_cond:
            if not RESPONDER.ports_opened:
                logger.debug('Original thread stopped')
                RESPONDER.ports_open_cond.wait()
                logger.debug('Original thread resumed')

        remote_check_opts = ['--replica %s' % options.hostname]

        if options.auto_master_check:
            logger.info("Get credentials to log in to remote master")
            cred = None
            if options.principal is None:
                # Check if ccache is available
                try:
                    logger.debug('KRB5CCNAME set to %s',
                                 os.environ.get('KRB5CCNAME', None))
                    # get default creds, will raise if none found
                    cred = gssapi.creds.Credentials()
                    principal = str(cred.name)
                except gssapi.raw.misc.GSSError as e:
                    logger.debug('Failed to find default ccache: %s', e)
                    # Use admin as the default principal
                    principal = "admin"
            else:
                principal = options.principal

            if cred is None:
                (krb_fd, krb_name) = tempfile.mkstemp()
                os.close(krb_fd)
                configure_krb5_conf(options.realm, options.kdc, krb_name)
                global KRB5_CONFIG
                KRB5_CONFIG = krb_name
                (ccache_fd, ccache_name) = tempfile.mkstemp()
                os.close(ccache_fd)
                global CCACHE_FILE
                CCACHE_FILE = ccache_name

                if principal.find('@') == -1:
                    principal = '%s@%s' % (principal, options.realm)

                if options.password:
                    password=options.password
                else:
                    password = installutils.read_password(principal, confirm=False,
                               validate=False, retry=False)
                    if password is None:
                        sys.exit("Principal password required")


                result = ipautil.run([paths.KINIT, principal],
                     env={'KRB5_CONFIG':KRB5_CONFIG, 'KRB5CCNAME':CCACHE_FILE},
                    stdin=password, raiseonerr=False, capture_error=True)
                if result.returncode != 0:
                    raise RuntimeError("Cannot acquire Kerberos ticket: %s" %
                                        result.error_output)

                # Verify kinit was actually successful
                result = ipautil.run([paths.BIN_KVNO,
                     'host/%s' % options.master],
                    env={'KRB5_CONFIG':KRB5_CONFIG, 'KRB5CCNAME':CCACHE_FILE},
                    raiseonerr=False, capture_error=True)
                if result.returncode != 0:
                    raise RuntimeError("Could not get ticket for master server: %s" %
                                        result.error_output)
                # Now that the cred cache file is initialized,
                # use it for the IPA API calls
                os.environ['KRB5CCNAME'] = CCACHE_FILE

            try:
                logger.info("Check RPC connection to remote master")

                xmlrpc_uri = ('https://%s/ipa/xml' %
                              ipautil.format_netloc(options.master))

                if options.ca_cert_file:
                    nss_dir = None
                else:
                    nss_dir = paths.IPA_NSSDB_DIR

                with certdb.NSSDatabase(nss_dir) as nss_db:
                    if options.ca_cert_file:
                        nss_db.create_db()
                        ca_certs = x509.load_certificate_list_from_file(
                            options.ca_cert_file)
                        for ca_cert in ca_certs:
                            nss_db.add_cert(
                                ca_cert,
                                str(DN(ca_cert.subject)),
                                certdb.EXTERNAL_CA_TRUST_FLAGS)

                    api.bootstrap(context='client',
                                  confdir=paths.ETC_IPA,
                                  xmlrpc_uri=xmlrpc_uri,
                                  nss_dir=nss_db.secdir)
                    api.finalize()
                    try:
                        api.Backend.rpcclient.connect()
                        api.Command.ping()
                    except Exception as e:
                        logger.info(
                            "Could not connect to the remote host: %s", e)
                        raise

                    logger.info("Execute check on remote master")
                    try:
                        result = api.Backend.rpcclient.forward(
                            'server_conncheck',
                            ipautil.fsdecode(options.master),
                            ipautil.fsdecode(options.hostname),
                            version=u'2.162',
                        )
                    except (errors.CommandError, errors.NetworkError) as e:
                        logger.info(
                            "Remote master does not support check over RPC: "
                            "%s", e)
                        raise
                    except errors.PublicError as e:
                        returncode = 1
                        stderr = e
                    else:
                        for message in result['messages']:
                            logger.info('%s', message['message'])
                        returncode = int(not result['result'])
                        stderr = ("ipa-replica-conncheck returned non-zero "
                                  "exit code")
                    finally:
                        if api.Backend.rpcclient.isconnected():
                            api.Backend.rpcclient.disconnect()
            except Exception as e:
                logger.debug("RPC connection failed: %s", e)
                logger.info("Retrying using SSH...")

                # Ticket 5812 Always qualify requests for admin
                user = principal
                try:
                    ssh = SshExec(user, options.master)
                except RuntimeError as e:
                    logger.warning("WARNING: %s, skipping ssh test", e)
                    return 0

                logger.info("Check SSH connection to remote master")
                result = ssh('echo OK', verbose=True)
                if result.returncode != 0:
                    logger.debug('%s', result.error_output)
                    raise RuntimeError(
                        'Could not SSH to remote host.\n'
                        'See /var/log/ipareplica-conncheck.log for more '
                        'information.')

                logger.info("Execute check on remote master")
                result = ssh(
                    "/usr/sbin/ipa-replica-conncheck " +
                        " ".join(remote_check_opts))
                returncode = result.returncode
                stderr = result.error_output
                logger.info('%s', result.output)
            if returncode != 0:
                raise RuntimeError(
                    "Remote master check failed with following "
                    "error message(s):\n%s" % stderr)
        else:
            # wait until user  test is ready
            logger.info(
                "Listeners are started. Use CTRL+C to terminate the listening "
                "part after the test.\n\n"
                "Please run the following command on remote master:\n"
                "/usr/sbin/ipa-replica-conncheck %s",
                " ".join(remote_check_opts))
            time.sleep(3600)
            logger.info(
                "Connection check timeout: terminating listening program")
    return 0


if __name__ == "__main__":
    try:
        sys.exit(main())
    except KeyboardInterrupt:
        logger.info("\nCleaning up...")
        sys.exit(1)
    except RuntimeError as e:
        logger.error('ERROR: %s', e)
        sys.exit(1)
    finally:
        if RESPONDER is not None:
            RESPONDER.stop()
            RESPONDER.join()
        for file_name in (CCACHE_FILE, KRB5_CONFIG):
            if file_name:
                try:
                    os.remove(file_name)
                except OSError:
                    pass
